A power amplifier in a mobile system may be placed in an extreme situation, such as a mismatched load, high input power, electrostatic discharge (ESD), etc., requiring a protection circuit capable of protecting same even under such extreme situations.
For instance, a power stage of a power amplifier may experience a high voltage swing as well as a high current swing in a failure zone. This means that the protection circuit should be operable in case of both voltage stress and current stress. However, existing protection circuits operate for either voltage stress or current stress only. Further, a protection circuit that employs a complicated structure including, e.g., operational amplifier may be difficult to implement, and may cause problems such as a delay due to the complicated structure.
Accordingly, there is a need to develop a protection circuit which has a simpler structure and is capable of protecting a power amplifier more effectively against both voltage stress and current stress.